Adult hypothyroidism is mostly seen in middle-aged women, with a ratio of 1:5 for both men and women, with insidious onset and slow progression. Fear of cold, little speech and weakness, indifferent expression, thick lips and large tongue, dry and cold skin, thinning of eyebrows and loss of the outer 1/3. Memory loss and mental retardation. Sinus bradycardia. Anorexia, abdominal distension, constipation. Decreased libido, impotence may occur in male patients, and overflowing breast in female patients. Typical symptoms General manifestations Fear of cold, dry skin with little sweating, coarse, thick, yellowish, and cold, sparse and dry hair, brittle and cracked nails, fatigue, drowsiness, poor memory, mental retardation, unresponsiveness, and mild anemia. Weight gain. Special facial features Pale and waxy face, puffy face, dull gaze, loose and swollen eyelids, indifferent expression, little speech, hoarse speech, slurred speech. Cardiovascular system The heart rate is slow, the heart sounds are weak, and the heart is generally enlarged, often with pericardial effusion, but also with swelling of myocardial fibers, deposition of mucus glycoproteins (PAS staining positive) and interstitial fibrosis after prolonged illness, called hypothyroid cardiomyopathy. The incidence of coronary heart disease is higher than that of the general population, but angina pectoris and heart failure rarely occur because of the low metabolic rate of peripheral tissues, reduced cardiac blood output, and reduced myocardial oxygen consumption. Sometimes blood pressure is high, but mostly diastolic. The electrocardiogram shows low voltage, T-wave inversion, widened QRS waves, and prolonged P-R interval. Digestive system Patients have loss of appetite, constipation and bloating, and even paralytic intestinal obstruction. About half of the patients have complete gastric acid deficiency. Muscle and joint system Muscle contraction and relaxation are slow and delayed, and muscle pain and stiffness are often felt. Bone metabolism is slow, and bone formation and resorption are reduced. The joints are painful and immobile, with a feeling of tonicity, aggravated by cold, as in chronic arthritis. Occasionally, joint cavity effusion is seen. Endocrine system Impotence in men, excessive menstruation in women, and amenorrhea in those who have not been treated for a long time. Low adrenocortical function, reduced blood and urine cortisol. Primary hypothyroidism may sometimes be accompanied by autoimmune hypoadrenocorticism and/or type I diabetes mellitus, called Schmidt syndrome.